Field of the Invention
The present invention relates to a wireless device, a gateway apparatus, and a wireless communication system.
Priority is claimed on Japanese Patent Application No. 2015-091887, filed on Apr. 28, 2015, the contents of which are incorporated herein by reference.
Description of Related Art
In recent years, a distributed control system (DCS) built in plants, factories, or the like has become a wireless system. That is, a distributed control system in which devices at a site (measures or operating devices) capable of wireless communication, called wireless field devices, and a control apparatus that performs control of the field device are connected over a wireless network has been built in plants or the like. A communication standard used for the wireless communication system that forms a basis of such a distributed control system includes, for example, an industrial wireless communication standard such as ISA100.11a or WirelessHART (registered trademark).
The wireless device such as the above wireless field device includes a connection port to which an external device (for example, a setting device) is connected, and various settings are performed by the external device connected to the connection port. For example, setting (provisioning) for causing the wireless device to participate in a wireless network, or various settings (for example, setting of a measurement range) regarding measurement when the wireless device is a measuring instrument are performed. The connection port included in the wireless device includes, for example, a serial port, a Universal Serial Bus (USB) port, and an infrared port.
In Japanese Unexamined Patent Application, First Publication No. 2007-74598 (hereinafter, referred to as Patent Document 1) and Japanese Unexamined Patent Application, First Publication No. 2008-160856 (hereinafter, referred to as Patent Document 2), a communication system that is not related to a wireless device installed in a plant, such as a wireless field device, but performs near field communication (NFC) is disclosed. Specifically, a technology capable of switching between NFC and BT communication (wireless short-range communication such as Bluetooth (registered trademark)) is disclosed in Patent Documents 1 and 2.
In order to perform various settings of the wireless device using the above-described external device, it is necessary for an operator carrying the external device to visit an installation location of the wireless device and connect the external device to the wireless device. When the wireless device is installed at a location in which a working environment is poor, such as a high place, it is necessary for the operator to perform work at the location in which the working environment is poor. Accordingly, workability and work efficiency become degraded.
Further, if it is necessary for the external device to be connected to the wireless device in a wired manner, complicated work for inserting a connection cable into the connection port of the wireless device is required. Thus, work efficiency becomes degraded. In addition, if the wireless device is installed outdoors, the connection port is likely to be exposed to wind and rain when the connection cable is connected to the connection port. Thus, a countermeasure for protection against dust or water is required.
Further, when a failure occurs in the wireless device, it is necessary for the wireless device in which the failure occurs to be replaced with a new wireless device, and for setting information of the wireless device in which the failure occurs to be handed over to the new wireless device. However, in a wireless device of the related art, even if a failure occurs in some of circuits (for example, a power supply circuit or a central processing unit (CPU)), it is often difficult to read the setting information, and replacement work is hindered. In a wireless device using a battery as a power supply, when there is no remaining charge in the battery, the setting information cannot be read.
In the wireless device using a battery as a power supply, for example, it is desirable for the power supply to be cut off by a hardware switch so as to prevent consumption of the battery when the wireless device is not used (for example, before installation at a site or during inspection of a facility). However, an operation of such a hardware switch may be difficult in an environment in which protection against water, dust, and explosion is required. Therefore, if a mechanism in which the wireless device is caused to enter a sleep state (low power consumption state) when the wireless device is not used, and the wireless device is awakened when use of the wireless device is initiated is provided, it is considered that problems associated with use of the hardware switch are not caused. However, since it is necessary to operate a circuit that detects a wake-up signal from the outside at any time during the sleep state, battery consumption increases.